These vanes, also known as projecting vanes, oppose vanes whose extremities are joined together by a holding ring. This latter conception is disadvantageous in that the holding ring is heavy and must not encumber the gas flow vein occupied by the vanes, which requires that it is housed in an annular hollow space of the adjacent piece, generally a rotor, for delimiting the vein which thus assumes a more complicated shape. But the projecting vanes do have the drawback of bending much more easily and thus vibrate during functioning of the machine of which they form part for permanent reasons, such as the characteristics of the flow of gases, or accidental causes, such as the passage of a foreign body, such as a bird. The vibrations affect the functioning and efficiency and may even destroy the vanes. This is why it has been suggested to more solidly fix the vanes by extending them at their base portion embedded in a ring for delimiting the flow vein beyond this ring and by embedding the vanes in a second ring concentric to the first one or by embedding the base portion situated beyond the ring in a dampening material.